In a variety of situations, there exist apertures with appurtenant covers, such as doors, windows, automobile hatchbacks, hoods, and trunks. For many of these apertures, it is frequently desirable to be able to maintain the appurtenant cover in an open or closed position. Springs are commonly used in the art to assist in closure of such a cover. However, the use of springs quite commonly allows the door or other cover to "slam" closed. This reduces the life of the door, causes unpleasant noises and harms objects that are within the path of the quickly moving door.
Conventional cylindrical opening and closing devices such as fluid (most commonly gas) or spring-biased cylinder/piston mechanisms are frequently utilized in the art to effect the opening and closing of a cover of an aperture in a smooth, attenuated manner or to support a door, hatch, or the like in an open position. It is often desirable to have repeated access to the opening and space therein and, therefore, necessary to brace the cylinder/piston mechanism. If the cylinder/piston mechanism is biased toward a closed position, the brace should act in a manner to preclude the mechanism's normal retraction. If, however, the mechanism is biased toward an open position, the brace should preclude any external force such as wind or application of weight from effecting a closure of the cylinder.
Even when a cylinder/piston mechanism is utilized to hold a cover open, the mechanism may close or retract due to various reasons. At times, external forces which are not applied by the user, such as wind or weight on a hatch or door, may act to close the hatch or door when a user desires to have it remain open. For example, snow or ice build-up on a hatchback and the accompanying weight can override the open bias of the cylinder/piston mechanism and cause it to close. The weight of the hatch, itself, is frequently more than the cylinder/piston mechanism is designed to hold open. Further, in cold weather, a gas cylinder/piston mechanism does not hold as well as it does in warmer weather. Another problem is that cylinder/piston mechanisms, as other mechanical devices, simply wear out with use and will not stay open. In automobiles more than a few years old, or those having frequently opened hatches, these mechanisms often will not remain open. Replacement mechanisms are expensive and thus it is desirable to have an inexpensive means to prevent a mechanism from closing.
In the prior art, a variety of devices have been utilized to assist in keeping the cylinder/piston mechanism in the extended or open position. One such device, used with horizontally mounted mechanisms, particularly with screen doors, consists of a washer that has a small protuberance on the edge adjacent to the cylinder. The inner diameter of this washer is slightly larger than the diameter of the piston and the washer encompasses the piston. When it is desired that the door remain in an open position, the washer can be moved, manually, to a position adjacent to the cylinder wherein the protuberance prevents the piston from retracting into the cylinder. However, this prior art device is not useful with a non-horizontally mounted cylinder, in that the washer may fall due to gravity.
U.S. Pat. No. 4,078,779, entitled "PNEUMATIC SPRING WITH MANUALLY RELEASABLE STOP," to Molders; and No. 4,430,770, entitled "DOOR OPERATING MECHANISM," to Niekrasz, et al., disclose devices which are utilized in preventing the closure of a cylinder/piston mechanism. The '770 patent discloses a hinge modification, which, by manual manipulation of the piston end to an alternate position, precludes the bias of the cylinder from retracting the piston within the cylinder. The '779 patent discloses a permanently attached sleeve which fits over both the piston and cylinder, and, by means of a spring-actuated turning device, couples with a pin attached to the cylinder to cause the cylinder to remain in a semi-extended position. Neither of these patents discloses a device for checking the closure of a bias cylinder with a readily attachable and detachable apparatus which may be used on either horizontally- or vertically-mounted, biased cylinders.